Metallurgical process



W. E GREENAWALT.

METALLURGICAL PROCESS.

MPLQCATION FILED JUNE 10.. 1918.

Patented Nov. 2, 1920.

2 SHEETS-SHEET 1.

IM'EM OK w. E GREENAWALT.

METALLURGICAL PROCESS.

APPLICATION FILED JUNE [0. 1918.

1,357,495, Patented Nov. 2, 1920.

2 SHEETSSHEET Z 16 WIT/155859, 4:

luvs/v TOR WILLIAM E. GREEI l'AWALT, 01? DENVER. COLORADO.

PATENT c rries.

METALLURGICAL PROCESS.

Specification 0! Letters Patent.

Patented Nov. 2, 1.920.

" Application filed June 10, 1918. Serial No. 289.255.

To ail whom it concern.

Be it known'that 1, Warrant E. GREENA- wAL'r, a citizen of the UnitedStates, residmg in the city and county of Denver and :State of Colorado,have invented certain new and useful Im rovements in MetallurgicalProcesses, 0 which the following is a specification.

- The invention has for its more immediate object the renderingharmless, or mitigating the evils, in the electrolysis of impureelectrolytes, especially electrolytes obtained from leeching'ores andcontaining salts of the variable valent elements.

This prooess'may be regarded as a continuation of m co-pend ngapplications, Sigriai No. 15,5 3, and Serial 0. 132,273, and. like thoseapplications, will be described more particularly in reference to thetreatment of copper ores, although it is not intended tolimit it to anyparticular use;

In the electrolysis of impure copper solutions, as for example thoseobtained from leaching copper oreswit'h an acid sulfate solution, thereis always present iron sulfate, which injuriously ali'ects theoperation.

Ferrous sulfate in the electrolyte is not particularly harmfuhbut theferric sulfate is hi hly detrimental.

f a solution of copper sulfate, containing ferrous sulfate, iselcetrolyzod, copper is deposited at the cathode while sulfuric acid andferric sulfate are produced at the anode, as shown by the followingequations:

1. (31130 +H O+Electrol sis:

*' 2 t y Cu+H,SO,+O

2. CuSO +2FeSO +Electrolysis:

I (lu-l-FeASOJ,

The ferric sulfate. finding its way to the cathode, combines with thedeposited copper, and is again reduced to the ferrous condition, thus: p

The lossofefiiciency due to this cause is more-or less proportional tothe amount of ferric-sulfate inthe electrolyte, and under certainconditions ma be very large. In aggravatedrases \the use of eilicicncymay be so great'that the copper is dissolved as rapidly as it isdeposite If, however, the ferric sulfate can hereduced at" the expenseof a comparatively cheap reducing a out, such as hydrogen sulfid or coper su lid, then acid is regenen, ated, and t e iron in the electrolyte,being reduced to the ferrous condition; loses its ability to combinewith the deposited cop'- per, as shown by the equations:

In the treatment of copper ores by solvent processes there are producedrich and lean copper solutions. The rich copper solutions usually resultfrom the application of the standard solution, while the lean coppersolutions usually result from the application of wash water to wash outthe soluble values from the ore after the rich solutions have beenwithdrawn.

Usually, if the rich solutions are electrolyzcd or not, the leansolutions are chemically precipitated and the precipitate so obtainedusually plays no further wart in the general metallurgical scheme. ne ofthe objects of this process is to use the sulfide precipitated from thelean, or from the foul solutions, to reduce, or eliminate, thedifliculties in the electrolysis of the rich solutions, and have as anend product for both, the pure electrolytic metal.

The process can best be described more in detail by referring to theaccompanying drawings, in which Figure 1. is a diagrain maticlongitudinal section, and Fig. 2, a diagrammatic plan, of the generalscheme and apparatus carrying it out. In the draw ings, 1 is a leachingvat, or other suitable apparatus, for applying an acid solution'to theore to dissolve the copper. The rich copper solution flows into thestorage tank 2, and forms the electrolyte. The lean copper solution, orwashwater, flows into the pump 20, and is elevated through the pipe-line21 to the weak solution storage tank 2 From tank 22 the lean solutionflows in a reguiated stream into the precipitator 23, in which thesolution is violently agitated, sp yed, or atomized, in the presence ofhydroge suitid,

produced in the hydrogen sulfid generator 24. The copper is precipitatedas the sulfid, with the simultaneous regeneration of acid, as set forthin the following equation:

The resulting sludge, consisting of the precipitated copper sulfid andregenerated Weak acid solution. flows into the separator in which thesulfid settlesby gravity and is worked toy". rd the central opening inthe bottom and into the distributing pipe line 26 by the rotatingmechanism Within the tank, while the clear supernatant solution flowsinto the oxidizer 28, through the pipe line 27. This oxidizer ispreferably an electrolyzer in which the oxygen released by theelectrolytic action, oxidizes any excess of hydrogen sulfid from thereducer, so that the excess cannot precipitate copper in the ore as themore or less insoluble sulfid, and also to convert the ferrous saltsinto the ferric condition, which is desirable, since ferric salts act onboth the sulfid and oxidized copper in the ore to bring it intosolution. It oxidation is not desired, the solution flows through theby-pass 29. The washwater after having its copper precipi tatcd and anequivalent of acid regenerated, and preferably also electrolyzed toconvert the ferrous salts into the ferric condition, stored in tank 30for re-use an acid wash on the ore. as desired.

The electrolyte having the copper in solution and containing ironusually in both the ferric and ferrous condition, flows from the storagetank 2 in a regulattal stream into the redu ing: unit 3, where theferric salts are converted to the ferrous salts by means of coppersullid. then to th electrolyzcrs 4, then to the reducing unit 5. to thesecond series of clcctrolyzcrs to the third reducing unit T. t the thirdseries of electro lyncrs and so on, until the electrolyte is solucicntlyimpoverished in copper and rcgenerated in acid. The rcducinp unitsconsist of agitators, l, 5'. and. 7. ol' separators, 3 5 and 7". and ofair-lifts, l. and 1", or other device, for creating a return flow fromthe bottom of the separator to the top of the agitator. The coppersultid precipitate from the separator 25 is flowed in a regulated streaminto the agitators Il". 5", and 7, through the distributing pipe 26. TheElmtrolytc and copper sull'ld prccipitatc being in this way brought intointimate contact, the ferric salts are quickly reduced to the ferrouscondition. In order to make a clear separation of the precipitate andelectrolyte after reduction. the overflowing reduced soluti n. stillcontaining some copper sultid in suspeut n. i passed to the thicken rsor separators ii. and 7'. Where complete separation tak s place; theclear overflowing reduced solution going to the electrolyzers 4, (l, and8, while the settled precipitate at the bottom of the separators isreturned to the agitators. 3, 5, and 7. In this Way the copper sulfidprecipitate is consumed and the electrolyte reduced and enriched incopper sulfate, as shown by. equations 5 and 6. The electrolyzers 4, (l,and 8, are representative of a series of as many cells as desired.

The electrolyte on entering the cells is practically completely reduced.\Vhen electrolysis begins, copper is deposited at practically thetheoretical rate, while acid is regenerated according to equation 1, andsome of the ferrous salts converted to the ferric condition, accordingto equation 2. It is desirable to hold the ferric salts down to as lowas 0.109. ferric iron; it should not, in any event, greatly exceed 0.25%ferric iron.

This may be conveniently done by b ing the cells in compound series andby regulating the rate of flow through the system. The ferric salts,formed in alternate series of elcctrolyzers, is reduced in alternatereducers, and this is continued until the elec troiyte is suliicientlyimpoverished in copper and regenerated in. acid, when it flows into thepump 15, and through the pipe line 16 into the oxidizer and acidgenerator 17. This oxidizer is an electrolyzer in which the oxygenliberated by the electrolysis of the acid solution, oxidizes the ferrousiron to the ferric condition, so as to enable the solvent to act moreenergetically on the sultids in the ore. which are unattached bysulfuric acid. The solution may also ,be enrichcd in sulfuric acid byintroducing sulfur dioxid. from the sulfur dioxid generator 18, into theoxidizer 17. where it is oxidized by the action of the electric currentto sol furic acid. lfoxidatlon of the solution is not In-ccssary ordesired, it may be by-passcd through the pipe line 31, into the storagetank ill. In either case the rcgcm-ratcd acid solution is stored in tank1:7 to be applied to tho orc in the leaching vat, as desired. Thesulfuric acid acts on the oxids and carbunnies. and the ferric iron onthe sulfids. To this Way a. close extraction of the copper can bemade-usually closer than by ordinary acid leaching.

The copper sullid from the separator .25 may be directly distributed,through the pi pc line "26, to the agitators 3", ii, and T. It ispreferred, however. to introduce all the freshly precipitated coppersulfid into the first reducing agitator. 3*, and regulate the overflowin such a way that a. considerable portion of the copper sulfid flowsinto the separator 3, and then. as the settled sultid is elevated by theair lift t", pass it (in to the nest reducing agitator 5. Where thecycle is repeated. and then on to the next reducing agitator, 7, Wherethe cycle is again re posted, and so on for the entire series ofalternatc reducers and electrolyzcrs. \Vhon the impoverished sullidsludge; containing also considerable quantities of sulfur as shown byequation ilxissucs from the last 6 reducer, it is conducted to a filter38, and the M arid, and partially into the filtrate returned to thecircuit through the pipe '13, while the sludge goes to ihe roastingfurnace it) to have the Mil l'ur hurncd oil. and i the cupric sulfidpartially converted into the cuprous sulfid by the elimination of oneatom of sulfur. 'l he ouprous sulfid is more cllcctive in reducing theferric salts than the cupric sulfid. The sulfid precipitate, treated toeliminate some of its sulfur, is again put into the circuit 26 throughthe eonveycr in. The suli'ur dioxid from the furnace may be conducted,through i the pipe line ll to thioxidizers, and acid generators. 28 and17.

Instead of using air in the air lills. 3 5", and 7, it might bedesirable to introduce a gas into the air lift to act on theelectrolyte. Either sulfur rlioxid or hydrogen sullid may becfl'ectivcly intrruluced in this way. It niight be desirable lointroduce sulfur dioxid in the electrolyte in the first reducer, 3*, andthen maintain the ferric salts reduced with copper sulfirl in theremaining reducers.

A partial reduction of the variable valcnt salts'may be made with sulfurdioxid, by diverting some of the gas from the sulfur 'dioxid generator18, to the sulfur dioxid re ducer 4.8, shown in .2. 9.1Fe (S(),),,-i-S()-{-lLO:

' I QFeSO l-H SO Acid may be regenerated in this n ay from What wouldotherwise boa waste gas in many 'lnetallurgical works, while at the sametime reducing some of the t'crric salts.

The pro ess is applicahlc to chlorid as well as to sull'at solutions.

The reducing action of the precil'iitated copper sulfid. q iouitirc inboth hot and cold solutions. lnhot solutions containing 3.5 grams ferriciron per liter, (0.35% a at a temperature of 145-deg. R, withoccasionalstirring: under the same conditions, at

{52 deg. F., 56% of the ferric iron can he rei dncfld. Under the sameconditions, in either hot or cold solutions, the ferric iron can be 'com'iletcly reduced in one minute by violently shaking in a bottle orviolently agitating with air, when the amount of copper in fsuspensionis equal to that in solution; As "t" advisable to carry out theelectrolytic position at a temperature of about 125 F., there should beno trouble in having completely reduced electrolyte in the renccrs, andeffective depolarization in the cells, with considerably reduced powerfor do position.

"I claim:

1, A metallurgical rocess which consists copper and containing salts ofthe variable ralent elements to deposit the copper whereby thc salts ofthe variable valent elen'ients are raised from a lower to a highervalency, treating the lean copper solutions to prccipitate the metal astho sulfid, applying sulfur dioxid to the rich solutions, and thenmaintaining the solution reduced with the copper sulfid obtained fromthe lean solutions.

2. A metallurgical process which consists in applying sulfur dioxid to acopper solution obtained from leaching ores and oontaining salts of thevariable valent elements, clcctrolyzing the solution whereby the coppcris deposited and the salts of the variable ralen't elements raised froma lowcr to a higher valency, maintaining the electrolyte reduced withcopper sulfid until the electrolyte is suliiciently impoverished incopper and regenerated in the solvent, and then returning the clmtrolyleto the ore to dissolve more copper.

3. A process of clcctrolyzing a metal salt of a polybasic acid obtainedfrom leaching ores and containing salts of the variable valent elementswhich consists in alternately elcctrolyzii'ig and reducing theelectrolyte by adding copper sulfid as a reducing agent in the first ofthe series of reducers and then carrying a portion of the reducing agentfrom the first to the last of the series of reducers, and finallyseparating the impovof reducer-s and then carrying a portiono! thecopper sulfid from the first to the last of the series of reducers, andfinally separating the impoverished copper sulfid from the electrolyteimpoverished in copper and rturning the electrolyte to the ore andtreating the impoverished copper snlfid to reduce its sulfur content andagain treating the electrolyte therewith.

5. A process which consists in treating ores of copper with an acidsolution to dissolve. the metal, maintaining separate the rich and thelean ooppersolutions, electrolyzing the solutions rich in. copper andcontaining salts of the variable valent elements to deposit the copper,precipitating the cop per from the lean solutions with a chemicalprecipitant, applying the chemical precipiv tate to the electrolyte toreduce the higher valency salts formed by the electrolysis to a lowervalency, and then before returning the electrolyte to the oreelectrolyzing it under different conditions to convert the lower valencysalts to a higher valency.

6. A process which. consists in treating ores of copper with an acidsolution to dissolve the copper, maintaining separate the rich and thelean resulting copper solutions, electrolyzing the rich copper solutioncontaining salts of the variable valent elements to deposit the metal,precipitating the lean copper solutions with hydrogen sulfid, separatingthe sultid precipitate from the weak acid solution, applying the coppersulfid to the rich solution to maintain the ferric salts reduced, andoxidizing the precipitated lean solutions b electrolysis and returningthe regeneratet \veak acid solutions to the orc.

7. In the electrolysis of a solution of a 'metal salt of a polybasicacid obtained from leaching ores and containing salts of the variablevalent elements, theprocess which consists in applying sulfurdioxid tothe solution to reduce the salts of the variable "alcnt elements from ahigher to a lower valency in the first stages of the electrolysis, andthen continuing the reduction of the higher valency salts formed by theelectrolysis by means of copper sulfid precipitate, and then when thesolution is sufliciently impoverished in the metal being deposited andre generated in acid returning the solution to the ore.

8. In the electrolysis of a solution, of a metal salt of a polybasicacid obtained from leaching ores and containing salts of the variablevalent elements, the process which consists in applying sulfur dioxid tothe solution to reduce the salts of the variable valent elements from ahigher to a lower valency in the first stages of electrolysis, and thencontinuing the reduction of the higher valency salts formed by theelectrolysis by means of concentrated copper sulfid, and then when thesolution is suiliciently impoverished in the metal being deposited andres generated in acid returning the solution to the ore.

9. In the electrolysis of a solution of a metal salt of a polybasic acidobtained from leaching ores and containing salts of iron, the processwhich consists in electrolyzing the rich metal solutions to deposit themetal and regenerateacid and ferric salts, precipitating the metal fromthe lean solutions as the sulfid, applying the. metal sulfid precipitubeto the electrolyte to reduce the ferric I salts in the electrolyte andliberate sulfur from the precipitate, separating the residual recipitatefrom the electrolyte and reducmg its sulfur content, and then againapplying the precipitate reduced in sulfur to the electrolyte. A

It]. In the electrolysis of a solution of a metal salt of a polybasicacid obtained from leaching ores and containing salts of iron, theprocess which consists in withdrawing the electrolyte from theclcctrolyzcrs into )ools at different points of the system. treating thewithdrawn clm-troLytc at different points of the system with a solidrcdlwing agent distinct from the ore by agitation, returning the reducedelectrolyte to the electrolyzcrs, and finally when the electrolyte issufliciently impoverished in the metal being deposited and regeneratedin acid returning the solution to the ore.

11. In the electrolysis of a solution of a metal salt of a polybasicacid containing salts of iron, the process which consists in reducingthe ferric iron formed by the elec trolysis to the ferrous condition byapplying a reducing agent to a series of pools of the electrolyte,progressively advancing the electrolyte through a series ofelcctrolyzers, and progressively advancing the electrolyte through aseries of pools communicating with the electrolyzers and containing areducing agent for the ferric salts.

12. In the electrolysis of a solution of a metal salt of a polybasicacid containing salts of iron, the process which consists in reducingthe ferric iron formed by the electrolysis to the ferrous condit on byapplying a reducing agent to a series of pools of the electrolyte,progressively advancing the electrolyte through a series ofelcctrolyzcrs, progressively advancing the. electrolyte through a seriesof pools communicating with the electrolyzers and containing a reducingagent for the ferric salts, and progressively advancing the reducingagent through the series of pools of the electrolyte.

13. A metallurgical process which consists in treating ores of copperwith an acid solution to dissolve the copper, electrolyzing theresulting solutions rich in copper and containing salts of iron todeposit the cop er with the simultaneous oxidation of theerprecipitating the copper'from the leanand foul solutions with hydrogensulfid, separating the resulting copper sulfid precipitate from theprecipitated solution as a thick- -rous salts to the ferric condition,chemically ened sludge, and applying the copper sulfid precipitate inthe form of a sludge to the rich copper solutions to reduce the ferricsalts formed by the electrolysis to the ferrous condition.

i WILLIAM E. GREENAWAl/I. \Vitnesses MARY II. W'ooLsnY,

IRMA GREENAWALT.

